New classes of antibacterial agents are needed to address both the growing resistance of bacteria to present therapies and the general lack of efficacy of existing antibiotics against slow-growing organisms. Although bacterial infections were once considered well controlled, the threat posed by the emergence of multidrug-resistant organisms is now well accepted. Desirable characteristics for new antibacterial products include activity against drug resistant organisms, reduced propensity for resistance development, greater biological half-life in humans, reduced liability for allergic reactions, and broad spectrum antibacterial activity.